1. Field of the Invention
This invention relates to a refrigerant processing cartridge for the accumulator of an automotive air conditioning system. The cartridge has an integral evaporator pressure regulator, a desiccant chamber, and refrigerant and oil filtering capability.
2. Disclosure Information
Automotive air conditioning systems typically use a fluorocarbon compound as a refrigerant. An air conditioning compressor in the system compresses the refrigerant for delivery to an air conditioning condenser where the state of the refrigerant changes from a gas to a liquid. The outlet side of the condenser is connected via an expansion device to an evaporator, where the refrigerant changes state from a liquid to a gas. An air blower circulates air over the evaporator to the vehicle passenger compartment causing heat transfer to occur from the ambient air to the evaporator.
The outlet side of the evaporator in certain air conditioning systems is connected to an accumulator which contains a liquid-gas separator. The separator causes liquid components of the refrigerant to be separated from the gaseous component before the gaseous component is returned to the compressor. The accumulator also provides for recovery of lubricating oil contained in the refrigerant gas and for returning a metered amount of lubricating oil to the inlet side of the compressor for lubrication purposes. Because the accumulator is connected to the inlet side of the compressor, the reduced absolute pressure in the accumulator causes a portion of the liquified refrigerant to return to the gaseous state, whereupon it is returned to the inlet side of the compressor. An example of a prior art air conditioning accumulator is shown in FIG. 1 of the specification and described in U.S. Pat. No. 4,474,035, which is assigned to the assignee of the present invention.
The amount of liquid refrigerant retained in the accumulator of the present invention depends upon the conditions under which the system operates. Regardless, however, of the amount of liquid retained in the accumulator, the accumulator functions to allow only vapor to be returned to the compressor together with a very small metered amount of lubricating oil.
Prior art refrigeration units employing fluid compressors requiring accurate control frequently need both high pressure relief means and low pressure or low temperature electrical cut-off means. The latter involves deengergizing the compressor from its drive means if the pressure or temperature of the refrigerant gas falls below a predetermined value, such as when the temperature or pressure of the evaporator falls below a given level. Automobile air conditioning systems commonly use a refrigerant compressor driven by the automobile engine through an electromagnetic clutch with a coil. In one form of electromagnetic compressor clutch system a switch is provided having a refrigerant-filled capillary tube whose one end senses evaporator temperature. The other end of the tube connects with a refrigerant-filled bellows portion which includes an electrical switch. When the evaporator temperature falls below a predetermined value, the clutch of the compressor is deactivated. Upon the evaporator temperature increasing the clutch is reactivated. The cycling of the clutch on-and-off maintains the evaporator temperature above 32.degree. F. to prevent freezing of the evaporator.
Cycling of an air conditioning compressor clutch in order to prevent icing of the evaporator may produce undesirable vehicle surge because the on-and-off cycling of the compressor causes a fluctuation in the torque available from the vehicle's engine. If, on the other hand, an evaporator pressure control is employed to throttle the flow of refrigerant through the system, the need for excessive cycling of the compressor clutch may be eliminated. In the event that the refrigerant pressure control is housed within an accumulator according to the present invention, the accumulator will perform the function of both an accumulator and a pressure regulator.
Designers have employed a variety of schemes for arranging accumulators or oil separators for use with compressors. In the usual case, the working fluid of the system is circulated to the accumulator tank, where the vapor components are caused to rise in the tank and are drawn off through a filter. In some refrigerant systems all of the vapor passing from the accumulator or separator must first pass through the filter element. The following U.S. patents generally describe such types of accumulators or separators: U.S. Pat. Nos. 1,672,571; 3,633,377; 4,173,440; 4,289,461; and 4,553,906. Further, British Pat. No. 1,512,507 and German Pat. Nos. 2,720,214 and 3,506,433 describe similar systems for separating and filtering oil from the working fluid of a compressor. Each of these devices employs a single flow path for the working fluid being returned to the compressor. This is disadvantageous inasmuch as a blockage of the single flow path will cause failure of the refrigerating system.
U.S. Pat. No. 2,608,269 describes an oil separator for a refrigeration system in which all of the gases and oil entering the oil separator must first pass through a solid adsorbent block and then through a matted mesh strainer before passing out of the separator. This type of system as well as systems described in U.S. Pat. Nos. 4,331,001 and 4,509,340 suffer from a common deficiency inasmuch as the refrigerant may be subjected to an excessively high pressure drop occasioned by the requirement of passage along a single flow path through not only a screen element but also through a desiccant or dehydrator material. The latter two patents describe automotive air conditioning accumulator assemblies in which a cartridge including a desiccant material has an outlet extending from the cartridge at a right angle to the axis of the accumulator. These cartridges are not well suited, therefore, to automated assembly of the accumulators because the cartridges are not susceptible to axial insertion into the upper portion of the cylindrical housing of the accumulator.
Various types of evaporator pressure control valves have been used in conjunction with automotive air conditioning systems. U.S. Pat. No. 3,708,998 discloses a valve which is mounted externally of the accumulator. U.S. Pat. Nos. 3,858,407; 3,939,669; 3,942,332; and 3,955,375 each disclose an accumulator having an evaporator pressure regulator built into the outer casing of the accumulator.
It is an object of the present invention to provide an accumulator with a refrigerant processing cartridge including a pressure regulator for regulating the pressure within the evaporator of the air conditioning system.
It is yet another object of the present invention to provide an accumulator having a replaceable refrigerant processing cartridge with a pressure regulator, which cartridge may be replaced in the event that the pressure regulator ceases to perform properly.
It is yet another object of the present invention to provide an accumulator having a refrigerant processing cartridge with a pressure regulator, which cartridge may easily be assembled into the accumulator by automated assembly techniques.
It is yet another object of the invention to provide a refrigerant processing cartridge for use in the accumulator of an air conditioning system wherein the cartridge has a dual flow path for the refrigerant in order that the refrigerant will not be subjected to an unduly great flow restriction on its way through the accumulator.
It is an advantage of the present invention that a refrigerant processing cartridge equipped with a pressure control device according to this invention may be used to build families of refrigerant accumulators with varying performance characteristics through the substitution of cartridges having different pressure control settings.
Other objects, features and advantages of the present invention will become apparent through the following description of the invention.